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What is your Microsoft Teams Strategy

3 Ways to Integrate UCaaS with Teams

From a technical viewpoint, there are three possible ways to Integrate your UCaaS service with Teams:

  1. Cross Launch: This is when a purpose-built Teams app is used to launch an external SIP softphone that is running on a desktop computer.
  2. Twinning: This refers to the scenario when a call to a PBX extension is forked (also referred to as sim-ring), and one leg of the call rings a phone number that is pointed to a SIP trunk that connects to a Teams user via direct routing.
  3. Registration: This approach is the heart of the TeamMate solution, whereby a Teams user is made to register to a specific SIP identity on the UCaaS or PBX service.


Cross Launch 

Cross launch refers to the scenario where a purpose-built Teams app is used to launch an external SIP softphone that is running on a desktop computer.   When this method is used, none of the benefits inherent to using Teams as a real-time communications client are realized because Teams is simply a launchpoint for the external softphone.  Many of the early Teams integrations use the cross launch model.  As of early 2023 the Teams integrations using cross launch include Cisco Webex, Metaswitch Max and Alcatel Rainbow, among others.

Cross launch produces a superficial user experience. Essentially, the cross launch app  provides a bridge between the Teams application and the external softphone. When an outbound call is initiated within Teams, the cross-launch app will launch the external softphone and dial the number. However, all further interaction with the call is done through the external softphone and not within the Teams application.  For inbound calls, the external softphone rings as normal but there is no way to answer the call from within Teams, essentially forcing the user to move to the external softphone app.  While this approach allows for a basic integration between Teams and an existing UCaaS platform, it results in a disjointed user experience as workers have to constantly switch between Teams and the external softphone.

Further, cross launch apps will not work on mobile devices, which negates one of the primary benefits that organizations cite for adopting Teams.



Twinning is a UCaaS feature which allows ringing a primary device before the call is ‘twinned’ to other devices associated with the PBX user, usually an external number. Using twinning to ring an external number that is pointed to a trunk with Direct Routing makes it possible for the PBX to ring a Teams user in tandem with a PBX user.

While this method can work at a basic level, it is suboptimal for several reasons:

  • Features – Many of the PBX features that organizations rely on require a distinct registration to the  PBX as a user.   PBX features such as call parking, call transfer, presence, call queues, busy lamp field (BLF) and voicemail message waiting indicator (MWI) are lost if the PBX user is not explicitly associated with a unique SIP Registration.
  • Cost – Because twinning typically requires the use of a separate DID to which the extension call can be twinned, there are additional costs involved with maintaining the DID and the associated usage charges.
  • Complexity – Because twinning requires the administrator to provision a new SIP trunk for every PBX user, moves, adds and changes become substantially more complicated.  Likewise, troubleshooting is also more difficult because there is an extra call leg associated with every call to the PBX user.



Registration refers to the integration strategy whereby a Teams user is registered to the PBX or UCaaS provider as a distinct SIP extension.   This option yields the best strategy for UCaaS operators for these reasons:

Customer Experience

Registration results in the best customer experience, because users can realize the benefit of Teams without any trade offs.  They are able to make and receive calls that take full advantage of the Teams call control and media handling capabilities, yet still access all the features that they need from the PBX or UCaaS system.

Reduced Complexity

When compared to twinning, the registration approach greatly simplifies the integration process for UCaaS operators.  This is primarily because the UCaaS operator can treat Teams like any third-party softphone and use existing processes and personnel for provisioning, troubleshooting and support.


The TeamMate PBX Connector

Registration is the solution that TeamMate has implemented for UCaaS integration.  It achieves this through the use of a proprietary back-to-back user agent (B2BUA) that maps individual Teams users to a corresponding SIP extension.  It was purpose-built for UCaaS providers and PBX operators to be able to extend the existing PBX or UCaaS feature set to a Teams user.

In addition, it allows the PBX operator or UCaaS provider to fully manage and automate most setup and provisioning tasks. And, it has a built-in Teams app that gives users the ability to view in-call and post-call options that integrate with other Microsoft 365 applications for tasks such as adding a caller’s number to a contact or scheduling a follow-up meeting in Outlook.

Why Choose TeamMate

TeamMate Technology understands the unique technology challenges required to integrate your existing communications tools into Microsoft Teams.  We are dedicated to building integration tools that continue to push the boundaries of what is possible in Microsoft Teams with existing PBX and Trunk systems.

Microsoft Teams is accelerating its disruption of business calling, UCaaS, Conference Calling, PBX, and SIP Trunking.  In total an $54.8B (USD) market.  It is confusing to consider because Teams is, first and foremost, a Team Collaboration platform but its strength is that it provides many services together – unlike Zoom, Slack or the other competitors.  Service Providers who sell IT or PBX or SIP Trunks all need a strategy for how they will manage the flood of businesses asking for Microsoft Teams integration.  This is your Microsoft Teams Strategy.

Why Partner with TeamMate

Microsoft Teams integration is, ultimately, a feature that improves your your UCaaS and Microsoft Office 365 service.  You need a partner that you can rely on for technology and domain expertise.  Here are several reasons why TeamMate Technology is the right partner:

  • A full White Label solution.  You set up and manage all branding components.
  • A deep Knowledge Base of solutions to common and uncommon problems.
  • Hundreds of Service Providers and Resellers using TeamMate today for the integration.
  • Extensive functionality and branding in Microsoft Teams – unique in the market.
  • REST API to access all authentication and provisioning functionality.
  • TeamMate institutional expertise in SIP, Microsoft Graph API, and PowerShell.
  • We support PBX integration, SIP Trunk integration and (Q1 2021) SMS integration.
  • Using TeamMate it is easy to add Microsoft Teams as a softphone.  You should have this arrow in your quiver!

We are your TeamMates.

If you have any questions or need additional assistance, don’t hesitate. Reach out to us. 

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